Magnetoresistance effect device and method of production thereof

ABSTRACT

A method of production of a magnetoresistance effect device is able to prevent or minimize a drop in the MR ratio and maintain the high performance of the magnetoresistance effect device even if forming an oxide layer as a surface-most layer constituting a protective layer by the oxidation process inevitably included in the process of production of microprocessing by dry etching performed in a vacuum. Two mask layers used for microprocessing are doubly piled up. This method of production of a magnetoresistivity effect device including a magnetic multilayer film including at least two magnetic layers includes a step of providing under a first mask material that is a nonorganic material a second mask material able to react with other atoms to form a conductive substance, and a device made according to the method.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. application Ser. No.11/161,675, filed on Aug. 11, 2005, which claims priority to JapaneseApplication No. 2004-240838, filed on Aug. 20, 2004, the entire contentsof which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a method of production of amagnetoresistance effect device, more particularly, relates to a methodof production of a magnetoresistance effect device suitable forpreventing a drop in a magnetoresistance ratio.

2. Description of the Related Art

Magnetic random access memories (MRAMs) are integrated circuit magneticmemories that is now paid attention as memories having integrationdensities on a par with dynamic random access memories (DRAMs),featuring high speed performance on a par with static random accessmemories (SRAMs), and enabling unlimited rewriting. The magnetic randomaccess memories and magnetic heads are mainly comprised of layers ofnonmagnetic or magnetic thin films of several nm (nanometer) thicknessgiving a tunneling magnetoresistive (TMR) effect. This configurationwith the TMR effect is hereinafter referred to as “TMR devices”.

Further, each of the plurality of magnetic films forming a TMR device isformed by sputtering. The insulation layer is formed utilizing anoxidation reaction of a metal.

The basic structure of a TMR device is shown in FIG. 5. A TMR device 101is basically comprised, as explained above, of an insulation layer 102sandwiched at its two sides by ferromagnetic layers 103 and 104. Arrows103 a and 104 a show the directions of magnetization of theferromagnetic layers 103 and 104, respectively. FIGS. 6A and 6B are usedfor explaining the state of resistance in the TMR device 101 whenapplying a voltage V to the TMR device 101 by a DC power source 105. TheTMR device 101 has the feature of changing in resistance in accordancewith the states of magnetization of the ferromagnetic layers 103 and 104due to the DC voltage V applied from the DC power source 105. Further,as shown in FIG. 6A, when the directions of magnetization of theferromagnetic layers 103 and 104 are the same, the resistance value ofthe TMR device 101 becomes minimum, while as shown in FIG. 6B, when thedirections of magnetization of the ferromagnetic layers 103 and 104 areopposite, the resistance value of the TMR device becomes maximum. Theminimum resistance of the TMR device is indicated by “R_(min)”, whilethe maximum resistance of the TMR device 101 is indicated by “R_(max)”.Here, in general, there are a “current-in-plane” (CIP) structure sendinga sense current in parallel to the plane of the device film and a“current perpendicular to plane” (CPP) type sending a sense current in adirection perpendicular to the plane of the device film. FIG. 5 andFIGS. 6A and 6B show an example of a CPP type magnetoresistance effectdevice.

A “MR ratio (magnetoresistance ratio)” is defined for the above TMRdevice 101 as follows:MR ratio=(R _(max) −R _(min))/R _(min)  (1)

Next, the conventional method of production and problems of a TMR devicehaving the above multilayer structure and resistance characteristicswill be explained from the viewpoint of the deterioration of the MRratio.

A magnetoresistance effect device like a TMR device built into an MRAMor magnetic head is microprocessed in the process of production. Forexample, when etching the magnetic layers forming the TMR device, anetching gas of a mixed gas of carbon monoxide and a nitrogen compound(for example, NH₃: ammonia) (CO+NH₃) or an alcohol-based etching gasincluding hydroxy groups (CH₃OH) etc. is used. At this time, if using aresist mask made of an organic material for the etching, no selectivitycan be obtained and microprocessing is not possible, so the practice hasbeen to use tantalum (Ta), titanium (Ti), etc. giving selectivity withrespect to the magnetic layers as a hard mask and etch by reactive ionetching (RIE) etc. In particular, Ta is originally used as a thin filmmaterial forming part of a TMR device and has the advantage that it canbe deposited by the sputtering method in the same step as anothermagnetic material (see Japanese Patent No. 3131595, Japanese PatentPublication (A) No. 2002-38285, and Japanese Patent Publication (A) No.2001-274144).

However, if using Ta, Ti, etc. as a hard mask for etching by theabove-mentioned gases, the oxygen contained in the gases reacts with thesurface of the hard mask to form oxide films at the surface-most layerof the hard mask. This state will be explained with reference to FIGS.7A to 7C. FIGS. 7A to 7C show the conventional process of dry etching ofthe TMR device 101 provided with a Ta layer 111 as the layer forming thehard mask. In the TMR device 101, in particular reference numeral 112shows a substrate and 113 a bottom electrode.

In FIGS. 7A to 7C, the resist 114 is used to etch the Ta layer 111 toform a hard mask of the Ta layer 111. In the state of FIG. 7B, as aresult, a hard mask 111 a made of the Ta layer 111 is formed. In FIG.7B, the hard mask 111 a of the Ta layer 111 is used for etching thelayers forming the TMR device. At this time, the above-mentioned gasesare used. In FIG. 7C, an example of the state where the TMR device 101is etched using the hard mask 111 a of the Ta layer 111 is shown. Inthis example, the free layer 115 and barrier layer 116 are etched andthe hard mask 111 a of the Ta layer 111 is left at a thickness of tensof Å on the free layer 115.

In the conventional dry etching method explained above, finally the hardmask 111 a of the Ta layer 111 is left as a surface layer at the topmostlayer of the TMR device 101. After this, the TMR device 101 finishedbeing microprocessed in the vacuum dry etching apparatus is taken out ofthe dry etching apparatus, that is, is exposed to the air. Therefore,the TMR device 101 is placed in an environment in contact with oxygencontained in the air. Accordingly, by not removing all of the Ta layerused as the hard mask in the etching, but leaving some of it, this isgiven the role of a protective layer protecting the magnetic layers fromoxidation etc. As a result, the surface-most layer of the remaining hardmask 111 a of the Ta layer 111 inevitably reacts with the oxygen in theair in the step of transfer from the vacuum microprocessing to the air,even if not using an etching gas containing oxygen atoms as explainedabove, and forms an oxide film (or oxide layer) 117 at the surface-mostlayer where the hard mask contacts the oxygen.

However, if the oxide film 117 is formed at the surface-most layer ofthe hard mask 111 a of the Ta layer 111, the oxide film 117 becomes aninsulation layer. If the insulation layer is formed at the surface-mostlayer of the TMR device 101, a parasitic resistance ends up beingformed, so the above-mentioned MR ratio falls. This drop in the MR ratiois more striking with a TMR device of the CPP type, that is, the typeshown in FIGS. 7A to 7C, sending a sense current in a directionperpendicular to the plane of the device film, compared with the CIPtype sending a sense current in a direction parallel to the plane of thedevice film. Therefore, it is necessary to remove the oxide film 117 atthe surface-most layer of the hard layer 111 a of the Ta layer 111 toprevent a drop in the MR ratio, but as explained above, it is necessaryto protect the free layer 115 from oxygen in the air when transferringthe TMR device finished being microprocessed by etching to the outsideof the dry etching apparatus. This problem similarly occurs when usingTi as a hard mask instead of Ta.

The TMR device after microprocessing is exposed once to the air, thentransferred to the next step of production for forming electrodes etc.

Further, as related art of the present invention, there are the thinfilm device and method of production of the same disclosed in JapanesePatent Publication (A) No. 2001-28442. The thin film device and methodof production of this publication relate to a magnetic head and a methodof production of a magnetic head and mainly has as its object formationof lead electrodes by highly selective dry etching without damaging(etching) the GMR.

OBJECTS AND SUMMARY

It is an object of the present invention to prevent the hard mask leftas the protective layer after the microprocessing by dry etching frombeing oxidized in the conventional method of production of a TMR deviceor other magnetoresistance effect device and as a result an insulationlayer being formed and a drop and deterioration of the MR ratio beingcaused.

An object of the present invention is to provide a method of productionof a magnetoresistance effect device able to prevent or minimize a dropin the MR ratio and maintain the high performance of themagnetoresistance effect device even if forming an oxide layer as asurface-most layer constituting a protective layer by the oxidationprocess inevitably included in the process of production ofmicroprocessing of dry etching performed in a vacuum, without making anyspecial changes to the process of production, by doubly piling up twomask layers used for microprocessing. That is, an object of the presentinvention is to provide a method of production of a magnetoresistanceeffect device capable of positively utilizing the protective layer withthe oxide layer formed through the production process as a layer formedby conductive oxide substance.

A method of production of a magnetoresistance effect device isconfigured as follows for achieving the above object.

The method of production of the magnetoresistance effect device is amethod of dry etching used for production of a magnetoresistance effectdevice comprised of a magnetic multilayer film including at least twomagnetic layers. This method comprises a step of providing under a firstmask material comprised of a nonorganic material a second mask materialable to react with other atoms to form a conductive substance so thatthe first and second mask materials make layers which are doubly piledup.

Among the above-mentioned magnetoresistance effect devices, in a TMRdevice sending a sense current in a direction perpendicular to the planeof the device film, when the surface-most layer of the protective layerreacts with for example oxygen atoms in the process of microprocessingby this dry etching apparatus, by using a material which does not forman insulator, but can form a conductor so as to form a protective layer,it is possible to prevent or minimize a drop in the MR ratio and forexample maintain the high performance of the MRAM, magnetic head, etc.formed by the TMR device.

Preferably, the second mask material is a material able to react withoxygen atoms to form a conductive oxide.

More preferably, the second mask material able to form a conductiveoxide is one of Ru (ruthenium), Rh (rhodium), Os (osmium), Nb (niobium),Ir (iridium), and Re (rhenium).

Still more preferably, the method further comprises a step of removingthe first mask material by an etching gas including oxygen atoms tochange the surface of the second mask material to the conductive oxide,and leaving the second mask material to form an electrode.

Still more preferably, the etching gas including oxygen atoms is a mixedgas of carbon monoxide and a nitrogen compound or an alcohol-based gasincluding at least one hydroxy group.

An embodiment of the present invention takes effect as follows. Whenmicroprocessing a TMR device or other magnetoresistance effect deviceused as a MRAM or magnetic head etc. by dry etching, since the secondmask layer is a material which can form a conductive substance, thesecond mask layer not completely removed, but remains after the firstmask material is completely etched away and forms an electrode servingalso as a protective layer, so a good sense current is obtained and ahigh MR ratio can be obtained.

Further, according to an embodiment of the present invention, by formingthe second mask material by Ru or another material able to form aconductive oxide, it is possible to completely remove the first maskmaterial in microprocessing by reactive ion etching (RIE) using apredetermined etching gas and not completely remove the second maskmaterial under it but leave it as a protective layer and thereby makethe surface-most layer a conductive oxide. It is possible to use this asit is as an electrode. Due to this, it is possible to eliminate thefilm-forming step of again forming an electrode after microprocessingthe magnetic material forming the magnetoresistance effect device.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other objects and features of the present invention willbecome clearer from the following description of the preferredembodiments given with reference to the attached drawings, wherein:

FIG. 1A is a structural view of a multilayer film showing an example ofthe structure of a conventional magnetoresistance effect device;

FIG. 1B is a structural view of a multilayer film showing an example ofthe structure of a magnetoresistance effect device according to anembodiment of the present invention;

FIGS. 2A to 2C are transition diagrams showing a dry etching process ina process of production of a magnetoresistance effect device accordingto an embodiment of the present invention;

FIG. 3A shows a table showing the resistivities of conductive oxides;

FIG. 3B shows a table showing the resistivities of single metals;

FIG. 4 is a view, obtained by experimental results, comparing the MRratio between the case of using a protective layer of Ru of anembodiment of the present invention and the case of using Ta of therelated art;

FIG. 5 is a longitudinal cross-sectional view showing the basicstructure of a TMR device of related art;

FIG. 6A is a view explaining the change of resistivity in theconventional TMR device;

FIG. 6B is a view explaining the change of resistivity in a conventionalTMR device; and

FIGS. 7A to 7C are transition diagrams showing a dry etching process ina process of production of a magnetoresistance effect device accordingto the related art and explaining problems in the same.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, preferred embodiments of the present invention will beexplained in accordance with the attached drawings.

FIG. 1A shows an example of the structure of a magnetoresistance effectdevice (TMR device) in a conventional production process(microprocessing step), and FIG. 1B shows, in comparison, an example ofthe structure according to an embodiment of the present invention.

In the example of the structure of a conventional magnetoresistanceeffect device (TMR device) 10 shown in FIG. 1A, a substrate 11 is formedwith a bottom electrode 12. The bottom electrode 12 is formed with amultilayer film comprised of eight layers forming the magnetoresistanceeffect device. This eight-layer multilayer film is comprised, from thebottommost first layer to the topmost eighth layer, magnetic layerspiled up or deposited in the order of “Ta”, “PtMn”, “a pinned layer”,“Ru”, “another pinned layer”, “a barrier layer”, “a free layer”, and“Ta”. The first layer (Ta) is the bottom layer, the second layer (PtMn)is an antiferromagnetic layer, the third layer to the fifth layer(pinned layer, Ru, and pinned layer) are pinned magnetization layers,the sixth layer (barrier layer) is an insulation layer, the seventhlayer (free layer) is free magnetization layer, and the eighth layer(Ta) is a hard mask forming a protective layer. The pinned magnetizationlayers, the insulation layer, and the free layer form an MR deviceportion 13.

In the example of the structure of a magnetoresistance effect device 20according to an embodiment of the present invention (FIG. 1B), asubstrate 11 is formed with a bottom electrode 12. The bottom electrode12 is formed with a multilayer film comprised of nine layers forming amagnetoresistance effect device. This nine-layer multilayer film iscomprised, from the bottommost first layer to the topmost ninth layer,of magnetic layers piled up or deposited in the order of “Ta”, “PtMn”,“a pinned layer”, “Ru”, “a pinned layer”, “a barrier layer”, “a freelayer”, “Ru (200 Å)”, and “Ta”. The first layer to the seventh layer andthe ninth layer are the same in configuration as in the multilayerstructure of the conventional magnetoresistance effect device (FIG. 1A)explained above. That is, the first layer (Ta) is the primer layer, thesecond layer (PtMn) is an antiferromagnetic layer, the third layer tothe fifth layer (pinned layer, Ru, and pinned layer) are pinnedmagnetization layers, the sixth layer (barrier layer) is an insulationlayer, the seventh layer (free layer) is a free magnetization layer, andthe ninth layer (Ta) is a hard mask forming a protective layer. In thismagnetoresistance effect device, the Ta of the topmost ninth layer isused as a hard mask, a TMR device portion 13 is formed by the pinnedmagnetizations, insulation layer and free layer, and a magnetic head cap14 is formed by the eighth layer (Ru) and ninth layer (Ta). Themagnetoresistance effect device of this embodiment of the presentinvention includes the insertion, between the seventh layer (free layer)and ninth layer (Ta), of the Ru (ruthenium) layer 15 as a protectivelayer able to be used as an electrode. The thickness of the Ru layer ofthe protective layer 15 is 200 Å, for example.

Next, the dry etching process performed in a vacuum in the process ofproduction of the magnetoresistance effect device 20 shown in FIG. 1Bwill be explained with reference to FIGS. 2A to 2C. As the etchingapparatus, an ICP plasma apparatus having a one-turn antenna is used,the antenna is connected to a plasma high frequency power source for thesupply of high frequency power (hereinafter referred to as “sourcepower”), and the object being etched, that is, the wafer on which theTMR device portion is patterned, is supplied with a self bias voltage(hereinafter referred to as the “bias power”).

In the state shown in FIG. 2A, the topmost layer of the Ta layer 22 isetched using the resist 21 as a mask so as to create a hard mask (firstmask material) of the Ta layer 22. The etching conditions include aninternal pressure of the vacuum vessel of the processing chamber of 0.8Pa, a source power of 500 W, a bias power of 70 W, an etching gas ofCF₄, and a flow rate of 50 sccm (326 mg/min). In the state shown in FIG.2B, as a result, a first mask layer of a Ta layer constituting the hardmask 23 is formed. In FIG. 2B, next, the Ta layer of the hard mask 23 isused to etch part of the TMR device 13 for example. At this time, as theetching gas, for example, a mixed gas of carbon monoxide and a nitrogencompound (CO+NH₃) or an alcohol-based etching gas including a hydroxygroup (CH₃OH) is used. The etching conditions when using a mixed gas ofCO and NH₃ as an etching gas include an internal pressure of the vacuumvessel of the processing chamber of 0.6 Pa, a source power of 1000 W, abias power of 300 W, a flow rate of CO gas as the etching gas of 25 sccm(31.25 mg/min), and a flow rate of NH₃ gas of 75 sccm (57.0 mg/min).When using CH₃OH gas as the etching gas, the conditions include aninternal pressure of the vacuum vessel of the processing chamber of 0.4Pa, a source power of 1000 W, a bias power of 200 W, and a flow rate ofetching gas of 15 sccm (18.75 mg/min). In FIG. 2C, an example is shownof the state in which the TMR device portion 13 has been etched. In thisexample, after the free layer 24 and insulator (barrier layer) 25 areetched and the TMR device is etched, or when the TMR device is etched,the hard mask 23 of Ta is removed. Thereby, the Ru layer 15 is exposedas the surface-most layer on the free layer 24.

That is, since the selectivity of Ru with respect to Ta is about 10,when the thickness of the Ru layer of the protective layer 15 is forexample 200 Å, the Ta (hard mask) of the first layer is made about 20 Åso as not to leave the hard mask (Ta) when continuing etching using theRu layer as the second mask material. The dry etching process is endedleaving a thickness of the Ru layer 15 of tens of Å required forfunctioning as a protective layer.

Note that in accordance with the above dry etching process, in theprocess of the states shown in FIG. 2B to FIG. 2C, the above etchingprocess is sometimes performed down to the layer of Ta on the bottomelectrode 12 (selectivity with respect to Ru free layer, barrier layer,and pinned layers is about 1 to 4).

Here, in the dry etching process from the state of FIG. 2B to the stateof FIG. 2C, there are two methods for removing the hard mask 23 of Ta.The first method of removal is the method of preadjusting the thicknessof the hard mask 23 so that the hard mask 23 is completely removed whenthe etching ends when etching the TMR device as explained above. Thesecond method of removal is a method of not adjusting the thickness, butperforming the processing for completely removing the hard mask 23 afterending the etching of the TMR device.

In the process of production of the magnetoresistance effect device 20,after the dry etching process introducing oxygen into the etching gasesshown in FIGS. 2A to 2C, the magnetoresistance effect device 20 isexposed to the air, and the oxygen atoms in the air react with thesurface of the layer of Ru of the second mask material 15 to form thelayer of the oxide 26 (oxide film). This oxide 26 becomes a conductiveoxide due to the characteristics of the Ru.

The tables of FIG. 3A and FIG. 3B show respectively the resistivities(Ωm) of the conductive oxides and the resistivities (Ωm) of metalsalone. As shown in FIGS. 3A and 3B, the conductive oxide of Ru, that is,RuO₂, has a resistivity substantially the same as the metal Ta alone.

Therefore, if using Ru as the second mask material 15 in the dry etchingprocess of the TMR device of the magnetoresistance effect device 20 andfinally completely removing the Ta of the first mask 23, there is theadvantage that a layer of a conductive insulator 26 is formed at thesurface-most layer in the process of production and the cause of thedrop in the MR ratio explained above can be removed. FIG. 4 shows acomparison of the MR ratio characteristic when using magnetoresistanceeffect devices of the same configuration from the substrate to the TMRdevice as in FIGS. 1A and 1B between the case of using Ta for thesurface-most layer becoming the protective layer after etching and thecase of making the Ru become the protective layer after etching as inthe embodiment of the present invention. The etching conditions, asexplained in the embodiment of FIGS. 2A to 2C, may be the conditions ofthe case of use of either a mixed gas of carbon monoxide and a nitrogencompound (CO+NH₃) or an alcohol-based etching gas including a hydroxygroup (CH₃OH), but they are made so that after etching, the thicknessesof the Ta and Ru remaining as the “free layer” protective layer on theTMR device become substantially the same (here 20-30 Å). As being clearby the comparison table shown in FIG. 4, the MR ratio when using the Ruof the second mask material as the protective layer is about three timesas many as the MR ratio when using the Ta instead.

Further, by finally completely removing the Ta of the first maskmaterial 23 in the dry etching process of the TMR device of themagnetoresistance effect device 20, a layer of a conductive oxide 26 isformed at the surface-most layer in the process of production, so thelayer of the conductive oxide 26 can be used as a top electrode.Therefore, there is the advantage that it is no longer required toprovide a step for forming the top electrode, which was required in theconventional production process.

As explained above, in the dry etching process of a TMR device in theprocess of production of the magnetoresistance effect device 20, thesecond mask material 15 of the magnetic head used is the material Ruable to react with oxygen atoms to form a conductive oxide, so thetechnical effect is exhibited of preventing or minimizing the drop inthe MR ratio and enabling the top electrode to be replaced with aconductive oxide.

As other materials having similar characteristics as the above Ru, Rh(rhodium), Os (osmium), Nb (niobium), Ir (iridium), and Re (rhenium) maybe mentioned. As described in the second row on of the table of FIG. 3A,the oxides Rh, Os, Nb, Ir, and Re, that is, RhO₂, OsO₂, NbO, IrO₂, andReO₃ also have sufficient conductivity. Note that FIG. 3B shows a tableof the resistivities of metals having conductivity for comparison.

Note that in the explanation of the above embodiment, an example of amaterial able to react with oxygen atoms to form a conductive oxide wasexplained, but of course it is also possible to similarly apply thebasic thinking of the present invention to a material able to form anitride or carbide having conductivity.

The configurations, shapes, sizes (thicknesses), and layouts explainedin the above embodiments are only shown schematically to an extentenabling the present invention to be understood and worked. Further, thenumerical values and compositions (materials) are only shown forillustration. Therefore, the present invention is not limited to theexplained embodiments and can be changed in various ways within thescope of the technical idea shown in the claims.

Further, as the etching apparatus, a helicon type apparatus called a“high density plasma source”, a two-frequency excitation parallel platetype plasma apparatus, a microwave type plasma apparatus, etc. may beutilized.

One object of the present invention is to prevent or minimize a drop inthe MR ratio in the production of a TMR device or othermagnetoresistance effect device.

The present disclosure relates to subject matter contained in JapanesePatent Application No. 2004-240838 filed on Aug. 20, 2004, thedisclosure of which is expressly incorporated herein by reference in itsentirety.

Although only preferred embodiments are specifically illustrated anddescribed herein, it will be appreciated that many modifications andvariations of the present invention are possible in light of the aboveteachings and within the purview of the appended claims withoutdeparting from the spirit and intended scope of the invention.

1. A method of production of a magnetoresistance effect device comprisedof a magnetic multilayer film including at least two magnetic layers,the method comprising: forming the magnetic multilayer film including aTa layer as a topmost layer and a protective layer immediately below andin contact with the topmost layer, wherein the protective layer is madeof any one of Ru (ruthenium), Rh (rhodium, Os (osmium), Nb (niobium, Ir(iridium), and Re (rhenium); forming a hard mask of Ta by etching the Talayer using a resist pattern, and thereafter; etching said protectivelayer and a layer under said protective layer by an etching gasincluding oxygen atoms through the hard mask of Ta and removing the hardmask of Ta so as to expose said protective layer as a topmost layerduring or after said etching.
 2. The method of production of amagnetoresistance effect device as set forth in claim 1, wherein saidetching gas including the oxygen atoms is a mixed gas of carbon monoxideand a nitrogen compound or an alcohol-based gas including at least onehydroxy group.
 3. The method of production of a magnetoresistance effectdevice as set forth in claim 1, wherein a surface of said protectivelayer is oxidized by said etching gas including the oxygen atoms.
 4. Amethod of production of a magnetoresistance effect device comprised of amagnetic multilayer film including at least two magnetic layers, themethod comprising: forming a protective layer on top of the at least twomagnetic layers, wherein the protective layer is made of any one of Ru(ruthenium), Rh (rhodium, Os (osmium), Nb (niobium, Ir (iridium), and Re(rhenium); forming a Ta layer as a topmost layer on the protectivelayer, such that the protective layer is immediately below and incontact with the topmost layer; forming a hard mask of the Ta layer byetching the Ta layer using a resist pattern; and thereafter, etchingsaid protective layer and at least one layer under said protective layerby an etching gas including oxygen atoms through the hard mask of Ta andremoving the hard mask of Ta so as to expose said protective layer as atopmost layer during or after said etching.
 5. The method of productionof a magnetoresistance effect device as set forth in claim 4, whereinsaid etching gas including the oxygen atoms is a mixed gas of carbonmonoxide and a nitrogen compound or an alcohol-based gas including atleast one hydroxy group.
 6. The method of production of amagnetoresistance effect device as set forth in claim 4, wherein asurface of said protective layer is oxidized by said etching gasincluding the oxygen atoms.